Control for laundry dryers



July 2, 1957 J A. ENGEL E-T AL 2,797,497

CONTROL FOR LAUNDRY- DRYERS Filed July 1, 1953 INVENTURS J ANTHONY ENGEL Jul-m E FLANNERY By HERBERT-BHULLAR ATTORNEY nited States Patent CONTROL .FQR LAUNDRY DRYER? J Anthony Engel, Salem, Ohio, and John P. Flannery and Herbert E. Hullar, Syracuse, N. Y., assignors, by mesa: assignments, to The Murray Corporation of America, Detroit, Mich, a corporation of Delaware Application July 1, 1953, Serial No. 365,356

Claims. (CI. 34-45.)

This invention relates to laundry dryers, and more particularly to a control circuit therefor.

In laundry dryers having a tumbling basket, an air heater and means for circulating heated air through the tumbling basket, it is desirable to provide dilferent operating temperatures, so that the dryermay operate efficiently and with a minimum amount of time upon laundry of different types, it being understood that some of the synthetic fabrics may be dried preferably at a lower temperature than cotton fabrics. It is further desirable to provide a timer control which may be set at will for any particular time, and at the end of which time, the source of heatmay be cut off and tumbling continued for a short period. Such dryers generally are provided with a .lint trap in the air outlet which, if not cleaned at proper intervals, tends to choke off the flow of air through the dryer, with the result that overheating might occur. The invention includes a thermostatic safety switch adapted to cut :off the heat should an undue temperature rise occur, and at the same time, provide a warning signal. The invention further relates to a doorswitch adapted to stop the tumbling action and cutoff the heat When such switch is opened. Further, the invention has to do with an electric .dryer adapted to operate on either a 110 ora 220 v. circuit, without any substantial alterations.

The above and other novel features of the invention will appear more fully hereinafter from the following detailed description When taken in conjunction with the accompanyingdrawings. It is expressly understood that the drawings are employed for purposes of illustration only and are not designed as a definition of the limits of the invention, reference being had for this purpose to the appended claims.

In the drawings, wherein like reference characters indicate like parts:

Figure 1 is a front elevational view of a dryer cabinet with the essential parts normally present therein indicated; and

Figure 2 is the control circuit for such dryer.

Referring to the drawings, there is shown :a cabinet having therewithin the usual stationary drum 12 and perforate tumbling basket 14. The tumbling 'basket l t has a front aperture 16 aligned with a front access door 18. On the drum 12 is an electric heater '20 adapted to heat air entering the drum. There is also provided the usual exhaust duct 22 coupled with a blower 24 adapted to exhaust air from the drum 12 into a lint trap indicated at 26. The basket 14 and the blower 24 are driven by a motor 28 through belt drives such as 30 and 32, respectively. The drum 12 is provided with illumination lamp 332 and an ultra violet ray germicidal lamp 34, both such lamps facing into the drum and illuminating the basket through the perforations thereof. An overload thermostat 36 is provided on the drum adjacent the air heater 20, such thermostat being adapted to cut ofl the power should an undue temperature rise 'occur as might result from a reduced air flow through the basket due to a clogged lint trap.

The outlet duct 22 is provided with two thermostats 38 and 40, sensitive to different temperature ranges, which thermostats normally control the flow of heated current to the heater 20 so as to maintain the outflow of air from the dryer within-one or the other of a given temperature range. The door 18 is adapted to actuate a door switch 42 of the single pole double throw type upon the opening or closure thereof, and the dryer is manually controlled through a manually settable timer 44 and a selector switch 46, the former for determining the length of the drying period and the .latter for determining the temperature range to be used during .the drying operation.

Referring to Figure 2, there is shown the usual 220 v. line connections 48 and 50 adapted to be connected to a 220 v. source, and a neutral v. connection 52. The line wires 48 and 50 lead into timer-actuated conu the circuit through such contacts being opened whenever the motor is stopped. Contacts 54 are connected to the other end of the electrical heater resistance 20, through one or both of two circuits 62 and 64. Circuit 62 contains therein the thermostat 38, which operates in the low range selected, and circuit 64 contains the thermostat 40, adapted to operate in the high range, circuit 64 additionally including a manual single pole single throw switch 46, which, when closed, placed both circuits 62 and 64 in parallel. In practice, the thermostat 38 will operate to cut off current when the temperature rises above and will turn on the current whenthe temperature drops below 120 F. Thermostat 40 is adapted to open the circuit upon a rise of temperature above 170, and to close the circuit whenever the temperature is below It will thus be seen that when .the switch 46 is closed, energization of the circuit to the heater resistance 2t) will be controlled by the thermostat 40, and when such switch is opened, control will be'had by the thermostat 38. Such thermostats may be of the well-known bimetallic biased disk type.

The motor 28 contains a field winding 70 and a starting winding 72. The field windingis connected by a lead '74 to the neutral terminal '52 on the one hand, and on the other hand, through a circuit 76 containing a fuse 78 and extending to the door switch 42. When the door is closed, a circuit is established through, such switch to the contacts 56, the switch being in the dotted position 42. The starting winding 72 is connected at one end to the lead 76 and through the centrifugal switch starting contacts 80 to the lead 74, it being understood that the circuit through such contacts 80 is opened as soon as the motor gains speed. The overload thermostat 36 is adapted to open .at any time that the temperature rises above 290 F., and such thermostat has in shunt therewith a high resistance signal device in the form of a buzzer 82, so that when such thermostat operates to open the circuit, a warning signal is provided which signal continues until the thermostat cools suiiiciently to reestablish the circuit.

The germicidal lamp 34- and the illuminating incandescent lamp 32 are connectedbetween the lead 58 and the neutral return 74, so that whenever the timer contacts 56 are closed, such lamps are energized. 'When the contacts 56 are open, as they would be at the completion of a drying cycle, it is desirable that the illuminating 3 lamp be energized for the removal of clothes, and an auxiliary circuit comprising the lead 84 connected between the line 50 and the door switch 42 operates to energize such lamps when the door switch is in the open position, as shown.

The timer may be of the spring escapement clockwork driven type, and comprises two earns 86 and 88 mounted on a clockwork driven shaft 92. The earns 86 and 88 actuate the contacts 54 and 56, respectively. The cams are shown in the off position, and are adapted to be rotated manually in a clockwise direction by the shaft knob 90 to such extent as would correspond to the length of time selected for a drying cycle, the rotation being through an arc of any selected angle, but necessarily less than 360. spring 94, after which rotation in a clockwise direction is controlled by the escapement 96, so as to gradually and automatically return the earns 86 and 88 to the off position as shown.

It will be observed that upon rotation of the cams 86 and 88 clockwise, the switches 54 and 56 will be closed by the cam rises 98 and 100, respectively, the switch contacts 56 being closed first and contacts 54 being closed subsequently. The effective angular spacing between the rises 98 and 100 is such that when the cam shaft 92 is being operated in a counterclockwise direction by the clock spring 94 as controlled by the escapement 96, contacts 54 will open approximately five minutes before contacts 56 are open. The timer is provided with stop means 97 to establish the off end position, and restrict rotation to less than 360 in setting. The timer may actuate a bell signal each time the 011? end position is reached to indicate that the drying operation has been completed.

Operation of the circuit will be readily understood from the foregoing description. However, if it be desired to dry synthetic fabrics which should not be unduly heated as compared to cotton fabrics, the switch 46 will be operated to the position shown in Figure 2, thereby placing the low range thermostat 38 in control. Thereafter, the clothes will be inserted into the tumbling drum, and the door closed, which operates the door switch so as to establish a circuit between the contacts 56 and the circuit 76 to the motor field. The knob 90 is rotated clockwise through such angle as may be desired to establish a drying period, thereby closing the timer-controlled contacts 54 and 56. Closing such contacts establishes a circuit through the motor field and the motor starting winding. As soon as the motor starts, the starting winding circuit is opened by the motor centrifugal switch, and thereafter, a circuit is completed by such centrifugal switch through the air heater resistance 20.

Should it be desired to add additional fabrics or garments to the tumbler, the door may be opened, thereby shifting the switch 42, to open the motor circuit 76. When the motor stops, the centrifugal switch will open the circuit to the air heater resistance 20, thus temporarily cutting ofi the heat; the tumbling drum will immediately stop; and the garments may be inserted. As soon as the door is closed, a circuit is reestablished to the motor field and starting winding, and when the motor starts, the starting winding circuit is opened, and the circuit to the air heating resistance coil 20 reestablished. The thermostat 38 will cut on and off the current to the resistanuce 20 in order to maintain a relatively constant temperature range within the outlet duct 22. When the timer approaches the end of the period, switch contacts 54 are opened, cutting off the current to the heater 20, and about five minutes thereafter, contacts 56 are opened, stopping the motor, and opening the circuit having lamps 34 and 32. Thereafter if the door is opened, the contacts 56 are shunted, closing the lamp circuit, but the door switch, at the same time opens circuit 76 to the motor.

Should the thermostat 36 reach the dangerous temperature of 290, by reason of reduced air flow, or from Rotation of the cam shaft 92 winds the clock some other cause, such thermostat will open the circuit from the contacts 56 through the centrifugal switch contacts 60 to open the circuit to the air heating resistance coil 20. The voltage across the thermostat when the thermostat is open due to excess temperature rise, will energize the warning buzzer 82 and provide a warning signal. It will be apparent from a consideration of the circuit that should a source of 220 v. be unavailable, the terminal 48 and the neutral terminal 52 may be connected together and the apparatus operated on v., a jumper 102 being the sole requirement. Under such circum stances, the drying time will be lengthened, but it will also be understood that the thermostat 38 or 40, whichever is in control, will be effective to maintain current fiow through the electrical resistance heater coil 20 for longer periods of time, in order to obtain a temperature of the exhaust air in the exhaust duct 22 within the temperature range of the particular thermostat 38 or 40 being used for control.

While a single embodiment of the invention has been illustrated and described, it is to be understood that the invention is not limited thereto. As various changes in the construction and arrangement may be made without departing from the spirit of the invention, as will be apparent to those skilled in the art, reference will be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

l. A laundry dryer comprising a cabinet, three terminals for connection to a 220 volt source of supply including two 220 volt terminals and a neutral terminal, a motor-driven tumbling drum, an access door and dooroperated switch, a manually settable timer having two circuits adapted to be opened in sequence at the end of a time cycle and connected respectively to said 220 volt terminals, a motor for driving said drum having a centrifugal starting switch and a centrifugal control switch closed when running, said motor being connected in series with the one of said circuits last to open and said door switch and said neutral terminal, a heating coil and thermostatic control circuit connected to the other timer circuit first to open and to said centrifugal control switch, said thermostatic control circuit comprising parallel branches, one including a low range thermostat, and the other a high range thermostat, and switch means for opening the circuit through said high range branch, said 220' volt terminal connected to the timer circuit first to open being adapted to be connected to the neutral terminal for 110 volt dryer operation.

2. A laundry dryer comprising a cabinet, three terminals for connection to a 220 volt source of supply including two 220 volt terminals and a neutral terminal, a motor-driven tumbling drum, an access door, a manually settable timer having two circuits adapted to be opened in sequence at the end of a time cycle and connected respectively to said 220 volt terminals, a motor for driving said drum having a centrifugal starting switch and a centrifugal control switch closed when running, said motor being connected in series with the one of said circuits last to open and said neutral terminal, a heating coil, a thermostatic control circuit connected to the other timer circuit first to open and to said centrifugal control switch, said thermostatic control circuit comprising parallel branches, one including a low range thermostat, and the other a high range thermostat, and switch means for opening the circuit through said high range branch, a drum illuminating lamp circuit energized by closure of the contacts of said circuit last to open, and a single pole double throw door-operated switch adapted to be connected in series with. said motor to open the motor circuit upon opening said door, and connected to said lamp circuit in parallel with said last-named contacts, to close said illuminating circuit when said door is open and said last-named contacts are open, said 220 volt terminal connected to the timer circuit first to open being 5 adapted to be connected to the neutral terminal for 110 volt dryer operation.

3. A laundry dryer comprising a cabinet, three terminals for connection to a 220 volt source of supply including two 220 volt terminals and a neutral terminal, a motor-driven tumbling drum, an access door, a manually settable timer having two circuits adapted to be opened in sequence at the end of a time cycle and connected respectively to said 220 volt terminals, a motor for driving said drum having a centrifugal starting switch and a centrifugal control switch closed when running, said motor being connected in series with the one of said circuits last to open and said neutral terminal, a heating coil, a thermostatic control circuit connected to the other timer circuit first to open and to said centrifugal control switch, and including a safety overheat thermostat adapted to open the circuit upon an undue temperature rise, said thermostatic control circuit comprising parallel branches, one including a low range thermostat, and the other a high range thermostat, and switch means for opening the circuit through said high range branch, a drum illuminating lamp circuit energized by closure of the contacts of said circuit last to open, a single pole double throw door-operated switch adapted to be connected in series with said motor to open the motor circuit upon opening said door, and connected to said lamp circuit in parallel with said last-named contacts, to close said illuminating circuit when said door is open and said last-named contacts are open, said 220 volt terminal connected to the timer circuit first to open being adapted to be connected to the neutral terminal for 110 volt dryer operation, and a high impedance signal device connected across said overheat thermostat, and energized upon the opening thereof.

4. A laundry dryer comprising a cabinet, three terminals for connection to a 220 volt source of supply including two 220 volt terminals and a neutral terminal, a motor-driven tumbling drum, a manually settable timer having two circuits adapted to be opened in sequence at the end of a time cycle and connected respectively to said 220 volt terminals, a motor for driving said drum having a centrifugal starting switch and a centrifugal control switch closed when running, said motor being connected in series with the one of said circuits last to open and said neutral terminal, a heating coil and thermostatic control circuit connected to the other timer circuit first to open and to said centrifugal control switch,

and including a safety overheat thermostat adapted to open the circuit upon an undue temperature rise within the drum, said thermostatic control circuit comprising parallel branches, one including a low range thermostat, and the other a high range thermostat, and switch means for opening the circuit through said high range branch, said 220 volt terminal connected to the timer circuit first to open being adapted to be connected to the neutral terminal for 110 volt dryer operation, and a high impedance signal device connected across said overheat thermostat.

5. A laundry dryer comprising a cabinet, three terminals for connection to a 220 volt source of supply including two 220 volt terminals and a neutral terminal,

\ a motor-driven tumbling drum, an access door and dooroperated switch, a manually settable timer having two circuits adapted to be opened in sequence at the end of a time cycle and connected respectively to said 220 volt terminals, a motor for driving said drum having a centrifugal starting switch and a centrifugal control switch closed when running, said motor being connected in series with the one of said circuits last to open and said door switch and said neutral terminal, aheating coil and thermostatic control circuit connected to the other timer circuit first to open and to said centrifugal control switch, and including a safety overheat thermostat adapted to open the circuit upon an undue temperature rise within the drum, said thermostatic control circuit comprising parallel branches, one including a low range thermostat, and the other a high range thermostat, switch means for opening the circuit through said high range branch, said 220 volt terminal connected to the timer circuit first to open being adapted to be connected to the neutral terminal for 110 volt dryer operation, and a high impedance signal device connected across said overheat thermostat.

References Cited in the file of this patent UNITED STATES PATENTS 439,392 Edison Oct. 28, 1890 2,037,062 Brach Apr. 14, 1936 2,486,315 Morris Oct. 25, 1949 2,505,041 Gorsuch Apr. 25, 1950 2,577,104 Butler Dec. 4, 1951 2,590,808 Wagner Mar. 25, 1952 2,654,961 Manecke Oct. 13, 1953 2.70 837 Robinson et al May 10, 1955 

